I've been beating my head into a wall with bed leveling and using G29. Searched all the articles, read up... just wasn't working. Tried manually leveling the bed and X-axis rail using my dial indicator. STILL couldn't get a level print of the first layer using G28 followed by G29 (left side of the bed would lay down a bead, the right side had the nozzle smearing). Gave up, removed G29 from the code alltogther, and used trial-and-error to tram the bed and move the Z-axes by hand until my first layer WAS level. Interestingly.... per the dial indicator, my bed is level BUT the X-axis rail is tilted (relative to the bed). But it prints level now!! Using: R1+, updated with a large LCD (updated Firmware using ROBO3DR1PLUSV2) and Cura 4.6.1 No idea what rev of Marlin though.